1. Field of the Invention
The present invention relates to high resolution electro-optical address by means of a luminescent device, and to electronic light valve imaging apparatus employing such address.
2. Description of the Prior Art
Recently, it has been found that light valve array devices provide a highly useful vehicle in electronic imaging. One preferred light valve configuration comprises a piece of ferro-electric ceramic material, such as lanthanum-doped lead zirconate titanate (PLZT), which is sandwiched between crossed polarizers and electrically activatable to operate in a Kerr cell mode. An array of such light valves comprises such crossed polarizers and a panel of PLZT material that has a plurality of electrodes formed on one of its major surfaces. The electrodes are arranged in a manner facilitating the selective application of discrete electrical fields across (in a direction perpendicular to the direction of viewing) discrete surface areas which constitute pixel portions of the panel. Upon application of such fields, the PLZT material becomes birefringent and changes the polarization of the incident light. This results in transmission of light through the PLZT pixels and cooperating polarizers varying as function of the respective addressing fields.
It can be appreciated that light valve arrays must address many image pixels per line in order to form images having even moderate detail. The number of pixels per line increases in accordance with the resolution requirements of the imaging application, e.g. becoming as large as 250 pixels per inch or larger for high quality continuous tone imaging. Because each pixel of the recording medium must be independently addressable with light in accordance with its unique picture content, discretely activatable electrode means are provided for each pixel portion of the light valve array. Each electrode means has had its own high voltage "off-on" switch (e.g. a transistor amplifier), and the cost and complexity of these many switches and their connection and packaging present problems.
One solution to minimize such problems is to provide a smaller number of transversely-spaced pixel portions in the light valve array and then effect multiple passes of the recording medium, with a transverse-indexing of the array (or recording medium) between passes. Thus, if light valve pixel portions are spaced with a three-pixel inter-space and the recording medium is transported past the light valve array four times, only one-fourth the usual number of high-voltage switches is required. However, multiple passes require additional time and can present registration problems.
Another solution, described in U.S. Pat. No. 4,374,397, entitled "Light Valve Devices and Electronic Imaging/Scan Apparatus with Locationally-Interlaced, Optical Addressing", filed June 1, 1981 in the name of J. M. Mir, employs cooperating high and low resolution light valve arrays to effect electronic imaging in an electronically efficient mode. This latter approach is highly advantageous for many applications; however, it is not highly light-efficient. In certain applications this can be a shortcoming.
Another solution, described in U.S. Pat. No. 4,377,753, entitled "High Resolution Optical-Addressing Device and Electronic Scanner and/or Printer Apparatus Employing Such Device" and filed June 1, 1981, in the name of J. M. Mir, provides optical-addressing device having: (i) a linear array of discrete lens elements each adapted to focus collimated light, from different incidence directions, onto respectively different pixel spots and (ii) control means for directing collimated light onto the linear lens array sequentially from the different incidence directions. The optical-addressing device cooperates with a linear light valve array of discrete, light-modulating portions which are each independently addressable to control passage of light and optically aligned with a respective one of the linear array elements.